North India 2014, much dust, more heat, late rain

The sweltering of North India, aggravated by manic urbanisation, just as manic use of personal automobiles, the steady thinning of tree canopies, and small businesses forced to buy diesel generators – in the tens of thousands, each emitting hot fumes that further trap already heated layers of sooty air – is an annual pre-monsoon epic that no-one has the energy to write.

This panel of four maps shows us where India baked during the last week of 2014 May (and now, Delhi has experienced a record its residents did not want). The high temperature belts (top left map), 40-45 Celsius, covered most of central and north-western India (Maharashtra, Madhya Pradesh, Gujarat, Rajasthan, Gangetic Uttar Pradesh, Haryana, Punjab and Delhi). Minimum temperatures (top right), 20-15 Celsius, are seen in two pockets – south interior Karnataka and in the North-East over Manipur and Mizoram.

These temperature maps may be read with the rainfall for the same period, 2014 May 25-31, to correlate particularly the temperature anomalies (how much higher or lower the normal maxima and minima have departed) with where it has rained. The rainfall map (lower left) shows rain having fallen over south Karnataka, but also north West Bengal and eastern Bihar, coastal Odisha and southern Haryana. These appear to relate to a group of anomalies (lower right): the first being interior Tamil Nadu, north-eastern Karnataka and adjacent Andhra Pradesh; the second being eastern Uttar Pradesh and adjacent Bihar. [You can get the four maps in this zip file.]

Read these from top left – 21, 22 and 23 June. Lower row – 24, 25 and 26 June. The green shading is the rain-bearing cloud cover. After 20 June the peninsula will have rain in most meteorological zone but North and north-west India will still await the monsoon system.

What these don’t show, but which the longer range forecast Indian Institute of Tropical Meteorology (Pune, Maharashtra) has on record, is that monsoon 2014 will not touch northern India until the fourth week of June. Rain-bearing cloud and wind systems will cover, in this forecast, peninsular India by around the 16th or 17th of June, but it will be another week before they deliver some relief to the cemented and asphalted surfaces of the National Capital Territory and its parched surroundings.

The Tropmet – as the Pune group is usually called – has bequeathed to us a definition (perhaps for this season only, subject to revision when climate change asserts itself) of monsoon rain that is in part scientific and in part geographic, which I think is a good sign (the Indian Meteorological Department will disagree, but we know better). The faster Tropmet decides to communicate in language appreciated, and understood, by Bharatiya citizens, the more said citizens will find an interest in correcting the misconceptions of scientists.

Tropmet says: “Rainfall within the summer monsoon season is mainly punctuated by the northward propagating monsoon intraseasonal oscillations (MISOs) with timescales of 30-60 days that manifests as spells of heavy rainfall and periods of quiescent rainfall, instead of a continuous deluge.” In the Konkan, we like our continuous deluge and the old-timers would have sixteen names for different sorts of deluge (and an equally rich chest of monsoon nouns for other sorts of rain).